My 99GT has a rought idle not too bad. I swap the spark plugs with some autolites 764 gapped at .54. It idles the same but now after I turn it on I let warm up for about 2 min. drive down the block and when I get to the stop it sorta wants to turn off but it doesn't. It runs fines..it pulls hard, & no problem with the car lighting up the tires. Its just when I get to the stop it doesn't idle too very smooth and it feels like it wants to turn off but it doesn't. Any ideas???? The car is Bone stock with 43K miles. Just changed out the fuel filter,pvc valve and spark plugs????